Saloon door support

ABSTRACT

A system for bracing a reciprocating shaft having a first shaft portion that moves along a long axis with respect to a second shaft portion and a short axis orthogonal to the long axis. The first shaft portion moves past a switch in a first direction to disengage the switch and past the switch in a second direction to engage the switch. A bracing member is carried by the switch and has a tip that, when the switch is engaged, is located immediately adjacent and laterally braces the second shaft portion by limiting movement of the second shaft portion along the short axis. When the switch is disengaged, the tip of the bracing member is not located immediately adjacent the shaft.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional PatentApplication No. 62/811,704, filed on Feb. 28, 2019, and entitled SALOONDOOR SUPPORT, which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The invention relates generally to supports for bracing a column that isunder compression to prevent buckling. More particularly, the presentinvention relates to swinging supports that move between a firstorientation for laterally bracing an axially reciprocating column and asecond orientation for allowing a portion of the column to move freelypast the supports without lateral bracing.

BACKGROUND OF THE INVENTION

Long slender columns, in the form of hydraulic (or pneumatic) cylinders,are often used in drilling operations, and, in the form of telescopiccranes, in lifting operations. For example, with reference to FIGS. 1-5,a mobile drilling apparatus 100 that may be used to drill holes intoground surfaces to produce oil wells, water wells, etc. is shown.

The drilling apparatus 100 includes a mobile base 102, such as a truck,and a drilling rig (or drilling mast or tower) attached to the base thatmay be raised to a vertical orientation when in use and lowered to asubstantially horizontal orientation when in transport. Among otherthings, the drilling rig includes a drill rod 101 having a drill bitlocated at its lower end (not shown) that is designed for cutting andgrinding in order to form holes in the ground. A rotary head 104 ismounted to the drill rod 101 and raises and lowers the drill rod duringthe drilling process. The rotary head 104 is raised and lowered duringthe drilling process by a hydraulic cylinder 103 that is mounted to therotary head. The hydraulic cylinder 103 includes a thin inner cylinderrod 105 that has a lower end 107 that is mounted to the mobile base 102.Throughout the drilling process, the inner cylinder rod 105 remainsstationary. A larger outer cylinder barrel 109 is placed over thecylinder rod 105 and moves upwards and downwards during the drillingprocess. The rotary head 104 described above is mounted to the outercylinder barrel 109, which carries the rotary head upwards or downwards.The rotary head 104 and cylinder barrel 109 are shown in a loweredposition in FIG. 4 and in a raised position in FIG. 5. The rotary head104 is slidably mounted to a pair of guide rails 111 located on eitherside of the outer cylinder barrel that guide the vertical motion of therotary head. During the drilling process, the hydraulic cylinder 103raises and lowers the rotary head 104, guided by the guide rails 111,and the rotary head 104 raises, lowers, and rotates the drill rod 101 tocreate a hole in the ground surface.

When designing drilling rigs, a primary design goal is to achieve thehighest force and longest stoke possible while minimizing the size andweight of the drill. This improves the speed and efficiency of welldrilling. However, the ground is often very hard and rocky and,therefore, a tremendous amount of pressure may be exerted on to thehydraulic cylinder 103 as it is raised and lowered. Long slendercolumns, such as the hydraulic cylinder 103, tend to buckle and caneventually fail if overloaded with axial compressive force. The maximumaxial compressive load that may be applied to a long, slender columnwhile the column remains straight and does not buckle (i.e., the“critical load”) can be determined using Euler's critical load formula.A simplified version of this formula is reproduced below, where P₁=thecritical load, E=the modulus of elasticity of the column material, I=theminimum area moment of inertia of the cross-section of the column, andL=the unsupported length of the column.

$P_{1} = \frac{\pi^{2}{EI}}{L^{2}}$

One way to increase the critical load and to reduce the likelihood of acolumn's buckling is to increase the size of the mechanical dimensionsof the column (e.g., outside diameter). Increasing the outside diameterof a column increases the moment of inertia (I) and, therefore,increases the critical load that the column can withstand before itbuckles. However, a disadvantage of increasing the outer diameter of thecolumn (such as the cylinder rod 105 in drilling operations) is that ittypically adds to the weight of the system, which adds to the cost andreduces speed of operation.

The critical load may also be increased by shortening the unsupportedlength of the column (L). This is implemented in certain drillingapplications by providing a support structure, such as a sliding rod orbarrel, between the ends of the thin cylinder rod 105. These supportskeep the cylinder rod 105 centralized (i.e., reduces lateral bowing)and, as a result, can drastically increase the axial compressive forcerequired to buckle the cylinder rod. As shown by the modified Eulercritical load equations shown below, if a support is located in themiddle of the span of the column, the force (P₂) required to buckle thatmid-point supported column will be four times the force required tobuckle an equivalent unsupported column. If the column is supported intwo places by a pair of supports located at ⅓ the length of the columnand ⅔ the length of the column, the force (P₃) required to buckle thethird point supported column will be nine times the force required tobuckle an equivalent unsupported column.

$P_{2} = {\frac{4\pi^{2}{EI}}{L^{2}}\mspace{14mu} \left( {{Mid}\text{-}{Point}\mspace{14mu} {Bracing}} \right)}$$P_{3} = {\frac{9\pi^{2}{EI}}{L^{2}}\mspace{14mu} \left( {{Third}\mspace{14mu} {Point}\mspace{14mu} {Bracing}} \right)}$

The inner cylinder rod 105 has a smaller outer diameter than the outerdiameter of outer cylinder barrel 109, so buckling is much more likelyto occur in the inner cylinder rod than the cylinder barrel. For thatreason, typically only the cylinder rod 105 is supported by additionalbracing. In many cases, only one support is used, and it is ideallyplaced in the middle of the unsupported length of the cylinder rod 105.However, the unsupported length of the cylinder rod 105 changes as thecylinder barrel 109 is raised and lowered over the cylinder rod. Forthat reason, the ideal location for placing the support to achieve themaximum benefit changes throughout the drilling operation.

One solution to this problem is to move the support along the length ofthe cylinder rod 105 until it reaches the desired position and to adjustthe position of the support during the drilling process. Onedisadvantage to using sliding supports is that a sliding or othersupport movement mechanism is needed to move the sliding support to theappropriate position along the cylinder rod 105. This sliding motioncauses wear to the system and often requires sealing to prevent hardcontaminants from lodging between the hydraulic cylinder rod 105 and thecylinder barrel 109, which would further increase abrasive wear andcost. Another disadvantage of using sliding supports is that their useoften requires the overall length of the cylinder rod 105 to beincreased, which increases its unsupported length and may reduce itsbuckling strength.

Accordingly, what is needed is a system and method for bracing a slendercolumn, such as a cylinder rod in a drilling rig, in one or morelocations along its length to increase its buckling strength (criticalload) without increasing the weight of the column and without causingexcessive wear to the column.

Notes on Construction

The use of the terms “a”, “an”, “the” and similar terms in the contextof describing the invention are to be construed to cover both thesingular and the plural, unless otherwise indicated herein or clearlycontradicted by context. The terms “comprising”, “having”, “including”and “containing” are to be construed as open-ended terms (i.e., meaning“including, but not limited to,”) unless otherwise noted. The terms“substantially”, “generally” and other words of degree are relativemodifiers intended to indicate permissible variation from thecharacteristic so modified. The use of such terms in describing aphysical or functional characteristic of the invention is not intendedto limit such characteristic to the absolute value which the termmodifies, but rather to provide an approximation of the value of suchphysical or functional characteristic.

Terms concerning attachments, coupling and the like, such as “connected”and “interconnected”, refer to a relationship wherein structures aresecured or attached to one another either directly or indirectly throughintervening structures, as well as both moveable and rigid attachmentsor relationships, unless specified herein or clearly indicated bycontext. The term “operatively connected” is such an attachment,coupling or connection that allows the pertinent structures to operateas intended by virtue of that relationship.

The use of any and all examples or exemplary language (e.g., “such as”and “preferably”) herein is intended merely to better illuminate theinvention and the preferred embodiment thereof, and not to place alimitation on the scope of the invention. Nothing in the specificationshould be construed as indicating any element as essential to thepractice of the invention unless so stated with specificity.

BRIEF SUMMARY OF THE INVENTION

The above and other needs are met by a system for selectively laterallybracing an elongate reciprocating shaft having a first shaft portion, asecond shaft portion, a long axis that extends through the first andsecond shaft portions, and a short axis that is orthogonal to the longaxis, wherein the first shaft portion is configured to move along thelong axis with respect to the second shaft portion. The system includesa first brace having a switch that is moveable between an engagedorientation and a disengaged orientation. A first contact portion of theswitch is configured to be contacted by the first shaft portion as thefirst shaft portion moves along the long axis past the switch in a firstdirection. As a result of that contact, the switch moves from theengaged orientation to the disengaged orientation. Additionally, asecond contact portion is configured to be contacted by the first shaftportion as the first shaft portion moves along the long axis past theswitch in a second direction and, as a result of that contact, theswitch moves from the disengaged orientation to the engaged orientation.A bracing member is carried by the switch and has a tip that, when theswitch is in the engaged orientation, is located immediately adjacentand laterally braces the second shaft portion by limiting movement ofthe second shaft portion along the short axis. When the switch is in thedisengaged orientation, the tip of the bracing member is not locatedimmediately adjacent the shaft.

Certain embodiments of the invention include a second brace. The firstand second braces are mounted together as a pair on opposing sides ofthe elongate reciprocating shaft and rotate simultaneously with oneanother between the engaged and disengaged orientations such that, inthe engaged orientation, the bracing member of the first brace limitsmovement of the second shaft portion along the short axis in a thirddirection and the bracing member of the second brace limits movement ofthe second shaft member along the short axis in a fourth direction. Incertain preferred embodiments, a semi-circular tip is formed on thebracing member. That semi-circular tip is located immediately adjacentthe second shaft portion in the engaged orientation. In those cases, thesecond shaft portion has a circular cross section and the semi-circulartip of the bracing member partially surrounds the shaft. Preferably, thesemi-circular tips of the first and second braces are mounted togetheras a pair on opposing sides of the elongate shaft and rotatesimultaneously with one another between the engaged and disengagedorientations such that, in the engaged orientation, the semi-circulartips of the bracing members substantially encircle the second shaftportion.

Certain embodiments of the invention include a rotation arrester forreleasably holding the switch at the disengaged orientation. Certainembodiments of the invention include a rotation limiter that limits thedegree of rotation of the switch as the first shaft portion moves alongthe long axis past the switch in the first direction and the seconddirection. In some embodiments, the rotation limiter limits the degreeof rotation of the switch such that, upon reaching the limit ofrotation, the switch is oriented in either the engaged orientation orthe disengaged orientation. In certain embodiments, the engagedorientation is offset by approximately 90 degrees of rotation from thedisengaged orientation.

Certain preferred embodiments of the invention include a bi-stableswitch that is automatically biased towards either the disengagedorientation or the engaged orientation when located between thedisengaged and engaged orientation. In those cases, the direction ofbias is determined by the rotational position of the switch. Preferably,the switch remains stationary when oriented in either the disengagedorientation or the engaged orientation. In certain embodiments, thebi-stable switch includes a first spring connected to a first arm or asecond arm of the switch for automatically biasing the switch to theengaged orientation. The bi-stable switch also includes a second springconnected to the other of the first arm and the second arm forautomatically biasing the switch to the disengaged orientation.Preferably, the switch is biased to the engaged orientation upon beingrotated towards the engaged orientation and beyond a point of maximumpotential energy stored in both the first and second springs. Also, theswitch is preferably biased to the disengaged orientation upon beingrotated towards the disengaged orientation and beyond a point of maximumpotential energy stored in both the first and second springs.

Other embodiments of the invention provide a bracing system thatincludes an elongate shaft having a first shaft portion in areciprocating relationship with a second shaft portion along a long axisthat extends through the first and second shaft portions and a shortaxis that is orthogonal to the long axis. In certain cases, the firstshaft portion and the second shaft portion are joined end to end andmove together as a single unit along the long axis. Preferably, thesecond shaft portion has a diameter that is smaller than a diameter ofthe first shaft portion.

A first brace includes a switch that is moveable between an engagedorientation and a disengaged orientation. The switch includes a firstcontact portion configured to be contacted by the first shaft portion asthe first shaft portion moves along the long axis past the switch in afirst direction and, as a result of that contact, the switch moves fromthe engaged orientation to the disengaged orientation. The switchfurther includes a second contact portion configured to be contacted bythe first shaft portion as the first shaft portion moves along the longaxis past the switch in a second direction and, as a result of thatcontact, the switch moves from the disengaged orientation to the engagedorientation. Lastly, a bracing member is carried by the switch. Thebracing member has a tip that, when the switch is in the engagedorientation, is located immediately adjacent and laterally braces thesecond shaft portion by limiting movement of the second shaft portionalong the short axis. Additionally, when the switch is in the disengagedorientation, the tip is not located immediately adjacent the shaft.

Certain embodiments include a second brace located adjacent the shaftand opposite the first brace. In those cases, the second brace rotatesbetween the engaged and disengaged orientations simultaneously with andin an opposite direction of rotation to the first brace. Preferably, inthe engaged orientation, the bracing member of the first brace limitsmovement of the second shaft portion along the short axis in a thirddirection and the bracing member of the second brace limits movement ofthe second shaft portion along the short axis in a fourth direction.

Certain embodiments of the invention include a spreader for assistingthe switch to rotate between the engaged orientation and the disengagedorientation. The spreader includes tapering sides that contact the firstcontact portions of both the first and second braces as the first shaftportion moves along the long axis past the switch in the firstdirection. The tapering sides also contact the second contact portionsof both the first and second braces as the first shaft portion movesalong the long axis past the switch in the second direction. Preferably,the first contact portions of the first and second braces are guidedalong the tapering sides as the first shaft portion continues to move inthe first direction, which automatically rotates the switch from theengaged orientation to the disengaged orientation. Additionally, thesecond contact portions of the first and second braces are preferablyguided along the tapering sides as the first shaft portion continues tomove in the second direction, which automatically rotates the switchfrom the disengaged orientation to the engaged orientation.

Certain embodiments of the invention include a position sensorconfigured to sense the position of the switch. In certain cases, acontroller for controlling an amount of pressured applied along the longaxis of the elongate shaft is provided. In those cases, a maximum amountof pressure that may be applied along the long axis of the elongateshaft is at least partially determined by the sensed position of theswitch. Preferably, the position sensor sends a signal to the controllerwhen an amount of pressure applied along the long axis of the elongateshaft for a selected position of the switch meets or surpasses apredetermined limit. That warning signal may trigger at least one of: anaudible alert generating by an audible alarm connected to the system, avisual alert generated by a visual alarm connected to the system, areduction pressure applied along the long axis of the elongate shaft, ashutdown of the system.

In order to facilitate an understanding of the invention, the preferredembodiments of the invention, as well as the best mode known by theinventor for carrying out the invention, are illustrated in thedrawings, and a detailed description thereof follows. It is notintended, however, that the invention be limited to the particularembodiments described or to use in connection with the apparatusillustrated herein. Therefore, the scope of the invention contemplatedby the inventor includes all equivalents of the subject matter describedherein, as well as various modifications and alternative embodimentssuch as would ordinarily occur to one skilled in the art to which theinvention relates. The inventor expects skilled artisans to employ suchvariations as seem to them appropriate, including the practice of theinvention otherwise than as specifically described herein. In addition,any combination of the elements and components of the inventiondescribed herein in any possible variation is encompassed by theinvention, unless otherwise indicated herein or clearly excluded bycontext.

BRIEF DESCRIPTION OF THE DRAWINGS

The presently preferred embodiments of the invention are illustrated inthe accompanying drawings, in which like reference numerals representlike parts throughout, and in which:

FIG. 1 illustrates a mobile drilling rig having an unsupported hydrauliccylinder;

FIGS. 2 and 3 are front and side elevation views, respectively,depicting a hydraulic cylinder having an inner cylinder rod locatedwithin an outer cylinder barrel;

FIGS. 4 and 5 illustrate a mobile drilling rig having a hydrauliccylinder in a lowered and raised position, respectively;

FIG. 6 is a front perspective view depicting a saloon door supportaccording to an embodiment of the present invention mounted to guiderails and in an engaged orientation supporting a cylinder rod of ahydraulic cylinder;

FIG. 7 is a front perspective view depicting the saloon door support ofFIG. 6 in an disengaged orientation to accommodate a larger cylinderbarrel of the hydraulic cylinder;

FIGS. 8-10 are front perspective views depicting a saloon door supportaccording to an alternative embodiment of the present invention, wherethe downwards movement of a hydraulic cylinder barrel rotates the saloondoor support from an engaged orientation to an disengaged orientation;

FIGS. 11-13 are rear perspective views of the saloon door support ofFIGS. 8-10;

FIG. 14 is a rear perspective view of a computer-monitored saloon doorsupport according to an alternative embodiment of the present invention;

FIGS. 15 and 16 are perspective views of a saloon door support having anasymmetrical oblong spreader and a switch that is magnetically held inengaged and disengaged orientations, respectively, according to anembodiment of the present invention;

FIG. 17 is a perspective view illustrating a split bushing mounted toeach of two supports of the saloon door support of FIG. 15; and

FIGS. 18A-18F are a series of front elevation views depicting anasymmetrical oblong spreader rotating adjacent supports of a saloon doorsupport from an engaged orientation to a disengaged orientationaccording to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

This description of the preferred embodiments of the invention isintended to be read in connection with the accompanying drawings, whichare to be considered part of the entire written description of thisinvention. The drawings are not necessarily to scale, and certainfeatures of the invention may be shown exaggerated in scale or insomewhat schematic form in the interest of clarity and conciseness.

Referring now to FIGS. 6 and 7, there is provided an elongate axiallyreciprocating shaft assembly 200 that includes a support system havingsaloon door-type motion for laterally bracing an elongate shaft.Although the invention is described herein using terms such as“vertical”, “upwardly” and “downwardly”, and similar terms which areconsistent with the orientations of the drawings, the reciprocalmovement described herein can be other than along a vertical line. Theelongate shaft in the embodiment of FIGS. 6 and 7 is formed by a firstshaft portion 202 and second shaft portion 204. The shaft includes along axis 206 that extends vertically through the first shaft portion202 and the second shaft portion 204 and a short axis (not shown) thatis orthogonal to the long axis. The first shaft portion 202 isconfigured to move axially along the long axis.

In the illustrated case, the first shaft portion 202 is hollow with anopening at the bottom end that is placed over one end of the secondshaft portion 204 such that the first shaft portion moves upwardly anddownwardly along the long axis 206 with respect to the second shaftportion, which remains fixed in place. The first shaft portion 202 isprovided with a lower mounting flange 220 and an upper mounting flange222. These flanges 220, 222 may be used to mount a rotary head (such asrotary head 104 depicted in FIG. 1) to the first shaft portion 202.

The assembly 200 includes a pair of braces (or supports 208) that aremounted to a support structure 210 located on either side of the shaft.The support structure 210 could be, for example, the guide rails 111shown in FIG. 1 and described earlier that are utilized in certaindrilling rig systems. Each support 208 includes a hinge-mounted switch212 that automatically rotates as the first shaft portion 202reciprocates upwardly and downwardly between an engaged orientation,where it laterally braces the shaft (FIG. 6), and a disengagedorientation, where it does not laterally brace the shaft (FIG. 7).

The switch 212 includes first contact portion 214 that, when the switch212 is in the engaged orientation, is configured to be contacted by aportion of the shaft as the first shaft portion 202 moves along the longaxis past the switch in a first direction. In this particular case, thefirst shaft portion 202 moves upwardly and downwardly with respect tothe second shaft portion 204 and the first direction is defined as adownward motion. However, the first direction could be any otherdirection (e.g., upward, leftward, rightward, etc.), depending on theorientation of the switch 212 and the shaft. The first contact portion214 is sized and configured to be contacted by lower mounting flange 220as the first shaft portion 202 moves downwards past the switch 212. As aresult of the contact between the first shaft portion 202 and the firstcontact portion 214, the switch 214 rotates from the engaged orientationto the disengaged orientation.

Similarly, the switch 212 includes second contact portion 216 that, whenthe switch 212 is in the disengaged orientation, is configured to becontacted by a portion of the shaft as the first shaft portion 202 movesalong the long axis past the switch in a second direction. In thisparticular case, the second direction is defined as an upward motion.However, the second direction could be any other direction (e.g.,downward, leftward, rightward, etc.), depending on the orientation ofthe switch 212 and the shaft. The second contact portion 216 is sizedand configured to be contacted by upper mounting flange 222 as the firstshaft portion 202 moves upwards past the switch 212. As a result of thecontact between the first shaft portion 202 and the second contactportion 216, the switch 214 rotates from the disengaged orientation tothe engaged orientation.

In addition to the first and second contact portions 214, 216, theswitch 212 also includes a bracing member that is carried by and rotateswith the switch between the engaged orientation and the disengagedorientation. In some cases, the bracing member is entirely separate fromthe first and second contact portions 214, 216 of the switch 212.However, in this case, the first contact portion 214 also functions as abracing member. When the switch 212 is in the engaged orientation, thebracing member extends towards the shaft and its outermost tip 218. Thetip 218 of the bracing member in this preferred embodiment issemi-circular in shape with a radius that is slightly larger than theradius of second shaft portion 204. The semi-circular tip 218 isconfigured to partially surround the circular second shaft portion 204of the shaft when the switch is in the engaged orientation. When theswitch 212 is in the engaged orientation, the tip 218 is locatedimmediately adjacent the second shaft portion. As a result of theproximity between the bracing member and the second shaft portion 204,the bracing member braces the shaft by limiting lateral movement of theshaft along the short axis. When the switch 212 is in the disengagedorientation, the bracing member (i.e., the first contact portion 214 inthis case) is rotated away from the shaft and its outermost tip 218 isnot located immediately adjacent the shaft and, therefore, does notlimit movement of the shaft along the short axis.

The switch 212 is designed to automatically rotate to the disengagedorientation when the first shaft portion 202 moves past the switch sothat the bracing member (i.e., first contact portion 214) does not bracethe first shaft portion 202. This design would be useful, for example,in drilling rigs where the first shaft portion 202 is a hydrauliccylinder barrel (such as hydraulic cylinder barrel 109 depicted in FIGS.2 and 3) that does not require bracing and the second shaft portion 204is a cylinder rod (such as hydraulic cylinder rod 105 depicted in FIGS.2 and 3) that does require bracing when placed under certain levels ofcompression. Unlike prior bracing methods, this support 208 is notmounted to the shaft itself and, therefore, does not add to the weightor the length of the shaft. Also, this support 208 is not moved alongthe shaft and, therefore, does not cause wear to the shaft. Instead, inpreferred embodiments, at least a portion of the shaft moves upwardlyand downwardly while the support 208 remains stationary. As discussed ingreater detail below, as a result of that reciprocating motion, theswitch 214 rotates to the engaged orientation only when bracing isrequired and rotates back to the disengaged orientation when bracing isnot required.

An alternative embodiment of an elongate reciprocating shaft assembly300 having a support system with saloon door-type motion for laterallybracing an elongate shaft is depicted in FIGS. 8-13. Like assembly 200,assembly 300 includes an elongate shaft having a first shaft portion302, second shaft portion 304, a long axis 306, and a short axis (notshown) that is orthogonal to the long axis. The first shaft portion 302moves axially along the long axis past one or more braces 308 that aremounted to a support structure (not shown) located on either side of theshaft. Each brace 308 includes a hinge-mounted switch 310 thatautomatically rotates as the first shaft portion 302 moves upwardly anddownwardly between an engaged orientation, where the brace laterallybraces the shaft, and a disengaged orientation, where it does notlaterally brace the shaft.

The switch 310 includes an L-shaped rotating member having a firstcontact portion 312 that, when the switch is in the engaged orientation,is configured to be contacted by a portion of the shaft as the firstshaft portion 302 moves downwardly. Similarly, the switch 310 includes asecond contact portion 324 that, when the switch is in the engagedorientation, is configured to be contacted by a portion of the shaft asthe first shaft portion 302 moves upwardly. More particularly, the firstand second contact portions 312, 324 are sized and configured to becontacted by a spreader device 314 that is mounted proximate the bottomof the first shaft portion 302 and that moves with the first shaftportion. Depending on the direction that the first shaft portion 302moves, the spreader device 314 assists in rotating the switch 310 eitherfrom the engaged orientation to the disengaged orientation or viceversa.

Separate spreader devices may be mounted to the shaft, where a firstspreader device assists in rotating the switch from the engagedorientation to the disengaged orientation and a second separate spreaderdevice assists in rotating the switch from the disengaged orientation tothe engaged orientation. In the embodiment shown, a singlediamond-shaped spreader device 314 assists in both. The spreader device314 includes first tapering sides 316 that contact the first contactportions 312 of brace 308 as the first shaft portion moves along thelong axis 306 past the switch in the first direction and second taperingsides 320 that contact the second contact portions 324 of the brace asthe first shaft portion moves along the long axis past the switch in thesecond direction.

When the switch is in the engaged orientation (FIGS. 8 and 11), thespreader device 314 assists in rotating the switch to the disengagedorientation. A first tapering side 316 preferably contacts the firstcontact portion 312 of the switch 310 to initiate the rotation process.From there, the first contact portion 312 is guided along the firsttapering side 316 to continue the rotation process. Similarly, when theswitch is in the disengaged orientation (FIGS. 10 and 13), the spreaderdevice 314 assists in rotating the switch to the engaged orientation. Asecond tapering side 320 preferably contacts the second contact portion324 of the switch 310 to initiate the rotation process. From there, thesecond contact portion 324 is guided along the second tapering side 320to continue the rotation process.

The spreader device 314 is preferably sized and configured toautomatically snap the switch 310 to the disengaged orientation beforethe first contact portion 312 reaches the end of first tapering side 316and to automatically snap the switch to the engaged orientation beforethe second contact portion 324 reaches the end of second tapering side320. In certain embodiments, the switch 310 is bi-stable (i.e., stablein two positions); therefore, when it is positioned between thedisengaged and engaged orientations, the switch is automatically biasedor rotated towards either the disengaged orientation or the engagedorientation. The direction of the bias is determined by the rotationalposition of the switch 310. On the other hand, the switch 310 remainsstationary when oriented in either the disengaged orientation or theengaged orientation. Advantageously, a bi-stable switch is always eitherfully disengaged or fully engaged and is preferably never partiallyengaged or partially disengaged.

The bi-stable switch 310 shown best in FIGS. 11-13 includes a firstspring 322 that is connected between first posts 332 for automaticallybiasing the switch to the engaged orientation once the switch is rotatedsufficiently far towards the engaged orientation. Similarly, thebi-stable switch 310 includes a second spring 326 that is connectedbetween second posts 328 for automatically biasing the switch to thedisengaged orientation once the switch is rotated sufficiently fartowards the disengaged orientation. The term “spring” should beinterpreted broadly to include not only springs but also magnets as wellas other similar devices that produce a sufficient strong enoughattractive or repulsive force to drive the switch to either the engagedorientation or disengaged orientation. The switch 310 is automaticallybiased to the engaged orientation upon being rotated towards the engagedorientation and beyond a point of maximum potential energy stored ineach of the first and second springs 322, 326. Similarly, the switch 310is automatically biased to the disengaged orientation upon being rotatedtowards the disengaged orientation and beyond a point of maximumpotential energy stored in both the first and second springs 322, 326.

For example, in FIG. 11, first spring 322 is minimally stretched and hasa minimal amount of stored potential energy (e.g., 20 units of potentialenergy), whereas second spring 328 is maximally stretched and has amaximal amount of stored potential energy (e.g., 70 units of potentialenergy). As the switch 310 is rotated counterclockwise (as shown in FIG.12), the amount of potential energy stored by first spring 322 increasesand the amount of potential energy stored by second spring 326decreases. At some equilibrium or tipping point in that rotation, theamount of potential energy simultaneously stored in each of the springs322, 326 will achieve a maximum value. That point might occur, when eachspring stores 45 units of potential energy. Further rotation beyond thatpoint will cause the switch 310 to immediately snap to the positionshown in FIG. 13. Once that happens, the potential energy stored byfirst spring 322 will increase, but the potential energy stored bysecond spring 326 will decrease.

In preferred embodiments, the switches 310 snap to either the disengagedorientation or the engaged orientation and securely hold the braces 308at those positions until a user moves them. To accomplish this, theswitches 310 may be provided with one or more rotation arresters, suchas pins, ball detents, or other similar devices that are suitable forholding one or more selected positions until acted upon by a sufficientforce. Additionally or alternatively, the switches 310 may be providedwith a rotation limiter that limits the degree of rotation of the switch310 as the first shaft portion 302 moves along the long axis past theswitch in both the first direction and second direction. Preferably,upon reaching the limit of rotation, the switch 310 is oriented ineither the engaged orientation or the disengaged orientation. Inpreferred embodiments, the rotation limiter includes an upper end 330that is contacted by the second contact portion 324 when the switch 310is in the engaged orientation (FIGS. 8 and 11) and a lower end 334 thatis contacted by the first contact portion 312 when the switch is in thedisengaged orientation (FIGS. 10 and 13). Through such contact, furtherrotation of the switch 310 is prevented. In this particular case, therotation limiter is sized and configured such that the engagedorientation is offset by approximately 90 degrees of rotation from thedisengaged orientation. In other embodiments, a greater or lesser degreeof rotation is allowed. A narrow center portion 336 comprises a notchthat connects the upper and lower ends 330, 334 and also provides roomfor the center portion of the switch 310 to be located. In preferredembodiments, the switch 310 is rotatably mounted to the rotation limiterwithin the center portion 336.

As mentioned previously, the presently-disclosed support system isdesigned such that the rotation between the engaged orientation and thedisengaged orientation occurs automatically as the shaft reciprocatesand only during certain portions of the reciprocation cycle. In thisparticular case, the switch 310 is automatically engaged only when thefirst shaft portion 302 is adjacent the switch and is automaticallydisengaged when the second shaft portion 304 is adjacent the switch.This configuration is particularly helpful in the case of drilling rigs,where one portion of the column (e.g., the cylinder rod 106) requireslateral bracing but another portion of the column (e.g., the cylinderbarrel 109) does not require lateral bracing. In this embodiment, theswitch 310 automatically rotates to the engaged orientation when bracingis needed (i.e., when the larger diameter first shaft portion 302 slidesupwards and exposes the narrower diameter second shaft portion 304) andautomatically rotates to the disengaged orientation when bracing is notneeded (i.e., when the larger diameter first shaft portion 302 slidesdown over the narrower diameter second shaft portion 304).

As mentioned earlier, if a column is supported mid-span, the criticalload increases to be four times the critical load of an unsupportedcolumn. However, if that same column is supported at two points located⅓ the length of the column and ⅔ the length of the column, the criticalload is increased to be nine times the critical load of an unsupportedcolumn. Therefore, the more support a column has, the higher itscritical load. Accordingly, with reference to FIG. 14, an improvedversion of a mobile drilling apparatus 100′ (originally shown in FIG. 1)is provided with a controller 400, such as a computer, for monitoring,at least partially controlling the operation of the drilling apparatus,or both, and a plurality of pairs of braces 308 mounted to the guiderails 111 adjacent both the thin inner cylinder rod 105 and larger outercylinder barrel 109 of hydraulic cylinder 103.

The braces 308 are automatically engaged to brace the inner cylinder rod105 and disengaged when the cylinder barrel 109 surrounds the cylinderrod as the cylinder barrel 109 moves axially with respect to thecylinder rod. The braces 308 in each pair are mounted on opposing sidesof the cylinder 103 and include switches that rotate simultaneously withone another between the engaged and disengaged orientations. Bothswitches include a bracing member for bracing the shaft when in theengaged orientation. The first (e.g., left, as shown in FIG. 14) brace308 of each pair limits movement of the cylinder 103 along the shortaxis in a first direction (e.g., leftwards) and the second (e.g. right,as shown in FIG. 14) brace of each pair limits movement of the shaftalong the short axis in a second direction (e.g., rightwards). Incertain embodiments, both bracing members have semi-circular tips suchthat, when the switch is in the engaged orientation, the semi-circulartips of the bracing members may substantially encircle a round shaft onall sides. As the column is raised and lowered, the braces automaticallyrotate between engaged and disengaged orientation.

In some embodiments, the braces 308 are provided with position sensorsthat sense the position of the switch (i.e., whether in the engaged ordisengaged orientation) and then send a signal back to the computer 400that indicates the position of the switches. Based on the position ofthe switches, the computer 400 may vary the amount of axial pressureexerted on the hydraulic cylinder 103. This would be beneficial, forexample, in the event that the braces 308 were in the disengagedorientation and the hydraulic cylinder 103 was not braced. As discussedabove, when a thin shaft is not braced, it can withstand lesser axialloads before buckling. Thus, in the above-described situation, thecomputer 400 would sense the position of the switches of the braces 308and would limit the axial load applied to the hydraulic cylinder 103 inorder to prevent the shaft from buckling.

The position signal sent by the sensor to the computer 400 may also beused for other purposes as well. For example, when an amount of pressureapplied along the hydraulic cylinder 103 for a selected position of theswitch meets or surpasses a predetermined limit, a warning signal mightbe triggered. More particularly, if the signal indicates that thehydraulic cylinder 103 is not braced, an audible or visual signal may betriggered once a predetermined amount of axial pressure is applied tothe shaft. Further, the signal might also automatically trigger areduction in the pressure applied to the hydraulic cylinder 103 as afurther safety precaution. Finally, the signal might trigger anautomatic shutdown of the entire system 100′ as a last resort.

Referring now to FIGS. 15 and 16, an alternative embodiment of anelongate reciprocating shaft assembly 400 having a support system withsaloon door-type motion for laterally bracing an elongate shaft isdepicted. Assembly 400 includes a pair of braces 408A, 408B that arestructurally and functionally similar to braces 308 discussed above.Braces 408A, 408B each include an L-shaped rotating member. The L-shapedrotating member of the left brace 408A includes a first contact portion412A and a second contact portion 424A. Similarly, the L-shaped memberof the right brace 408B includes a first contact portion 412B and asecond contact portion 424B. The first and second springs 322, 326 ofelongate reciprocating shaft assembly 300 (shown in FIGS. 11-13) arereplaced with magnets 432 in this alternative embodiment. Magnets 432are affixed to each of the brackets 408A, 408B and are located within amagnet housing 434 for redirecting the magnetic field of the magnet andstrengthening the effective magnetic attractive force. The magnets 432are designed to magnetically engage the L-shaped rotating member inorder to hold it in either the engaged position (FIG. 15) or disengagedposition (FIG. 16).

In FIG. 17, the back of the assembly 400 is shown to better illustratethe structure and arrangement of the braces 408A, 408B. The firstcontact portions 412A, 412B of each of the braces 408A, 408B includes apair of tips 440 (located in front of and behind shaft portion 404) thatare overlapped with corresponding pair of tips. To enable the tips 440to overlap one another, the braces 408A, 408B are vertically offset fromone another. In this case, brace 408A is located slightly below brace408B such that the tip 440 of first contact portion 412B overlaps thetip of first contact portion 412A. This overlapping configurationprovides added strength to the assembly 400 against buckling of shaftportion 404. In some embodiments, a split bushing half 442 is fixedlyattached to each of the first contact portions 412A, 412B. Each of thebushing halves 442 are semi-circular in shape so that, in combination,they completely encircle the shaft portion 404. The bushing halves 442closely approximate or even touch the shaft portion 404 in order toprovide greater resistance to lateral deflection. Preferably, to preventdamaging shaft portion 404, the bushing halves 442 are formed using amaterial that is softer than the shaft portion.

A single asymmetrical oblong-shaped spreader device 414 for assisting inrotating the L-shaped rotating member of braces 408A, 408B from theengaged orientation (Step “A”) through intermediate orientations(Positions “B”-“E”) to the disengaged orientation (Step “F”) when itmoves in direction 436 and also in rotating the L-shaped rotating memberfrom the disengaged orientation to the engaged orientation when movingin direction 438 is shown in FIGS. 18A-18F. Additionally, the shape ofthe spreader device 414 ensures that the overlapping tips 440 of thebraces 408A, 408B are correctly overlapped in both the engaged anddisengaged orientation.

The top and bottom of the spreader device 414 each include a pair ofrounded tapering sides, including a first side 416A having a top endthat is vertically offset below an adjoining top end of a second side416B. The first and second sides 416A, 416B are joined together at theirtop ends by a vertical lip 430. This structure is repeated on both thetop of the spreader 414 as well as the bottom of the spreader. The firstside 416A joins with the second side 416B on each of the left and rightsides of the spreader 414 at a point 444.

From position “A”, the spreader 414 travels downwards in direction 436towards the braces 408A, 408B, which are in the engaged orientation. Thetips 440 are overlapped with first contact portion 412B spacedvertically above first contact portion 412A. At position “B”, the bottomfirst side 416A of the spreader makes initial contact with the firstcontact portion 412B of brace 408B. Similarly, the bottom second side416B of the spreader 414 makes initial contact with first contactportion 412A of brace 408A. Through this contact, the braces 408A, 408Bbegin to rotate downwards. At position “C”, first contact portions 412A,412B slide along second side 416B and first side 416A, respectively, asthe braces 408A, 408B continue to rotate downwards as a result of thedownwards movement of spreader 414. As shown at positions “D” and “E”,as the spreader 414 continues downwards, the L-shaped members rotatepast an equilibrium point and automatically rotate further such that thesecond contact portions 424A, 424B come to rest on top of the top firstside 416A and top second side 416B, respectively. As shown at Position“F”, as the spreader 414 continues downwards, the top vertical lip 430and the positioning of the top first side 416A with respect to the topsecond side 416B, correctly causes the tip 440 of the second contactportion 424A to be located vertically below the tip of the secondcontact portion 424B. The steps are reversed to move the L-shapedrotating members of the braces 408A, 408B from the disengagedorientation to the engaged orientation as spreader 414 travels indirection 438.

Although this description contains many specifics, these should not beconstrued as limiting the scope of the invention but as merely providingillustrations of some of the presently preferred embodiments thereof, aswell as the best mode contemplated by the inventor of carrying out theinvention. The invention, as described and claimed herein, issusceptible to various modifications and adaptations as would beappreciated by those having ordinary skill in the art to which theinvention relates.

What is claimed is:
 1. A system for selectively laterally bracing anelongate reciprocating shaft having a first shaft portion, a secondshaft portion, a long axis that extends through the first and secondshaft portions, and a short axis that is orthogonal to the long axis,wherein the first shaft portion is configured to move along the longaxis with respect to the second shaft portion, the system comprising: afirst brace having: a switch that is moveable between an engagedorientation and a disengaged orientation; a first contact portionconfigured to be contacted by the first shaft portion as the first shaftportion moves along the long axis past the switch in a first directionand, as a result of that contact, the switch moves from the engagedorientation to the disengaged orientation; a second contact portionconfigured to be contacted by the first shaft portion as the first shaftportion moves along the long axis past the switch in a second directionand, as a result of that contact, the switch moves from the disengagedorientation to the engaged orientation; a bracing member carried by theswitch and having a tip that, when the switch is in the engagedorientation, is located immediately adjacent and laterally braces thesecond shaft portion by limiting movement of the second shaft portionalong the short axis and, when the switch is in the disengagedorientation, is not located immediately adjacent the shaft.
 2. Thesystem of claim 1 further comprising a second brace, wherein the firstand second braces are mounted together as a pair on opposing sides ofthe elongate reciprocating shaft and rotate simultaneously with oneanother between the engaged and disengaged orientations such that, inthe engaged orientation, the bracing member of the first brace limitsmovement of the second shaft portion along the short axis in a thirddirection and the bracing member of the second brace limits movement ofthe second shaft member along the short axis in a fourth direction. 3.The system of claim 1 further comprising a semi-circular tip formed onthe bracing member that is located immediately adjacent the second shaftportion in the engaged orientation, wherein the second shaft portion hasa circular cross section and the semi-circular tip of the bracing memberpartially surrounds the shaft.
 4. The system of claim 3 furthercomprising a second brace and semi-circular tips formed on the bracingmember of each brace, wherein the first and second braces are mountedtogether as a pair on opposing sides of the elongate shaft and rotatesimultaneously with one another between the engaged and disengagedorientations such that, in the engaged orientation, the semi-circulartips of the bracing members substantially encircle the second shaftportion.
 5. The system of claim 1 further comprising a rotation arresterfor releasably holding the switch at the disengaged orientation.
 6. Thesystem of claim 1 wherein the engaged orientation is offset byapproximately 90 degrees of rotation from the disengaged orientation. 7.The system of claim 1 further comprising a rotation limiter that limitsthe degree of rotation of the switch as the first shaft portion movesalong the long axis past the switch in the first direction and thesecond direction.
 8. The system of claim 7 wherein the rotation limiterlimits the degree of rotation of the switch such that, upon reaching thelimit of rotation, the switch is oriented in either the engagedorientation or the disengaged orientation.
 9. The system of claim 1further comprising a bi-stable switch that is automatically biasedtowards either the disengaged orientation or the engaged orientationwhen located between the disengaged and engaged orientation, wherein thedirection of bias is determined by the rotational position of theswitch, and wherein the switch remains stationary when oriented ineither the disengaged orientation or the engaged orientation.
 10. Thesystem of claim 9 further comprising: a first spring connected to afirst arm or a second arm of the switch for automatically biasing theswitch to the engaged orientation; and a second spring connected to theother of the first arm and the second arm for automatically biasing theswitch to the disengaged orientation, wherein the switch is biased tothe engaged orientation upon being rotated towards the engagedorientation and beyond a point of maximum potential energy stored inboth the first and second springs, and wherein the switch is biased tothe disengaged orientation upon being rotated towards the disengagedorientation and beyond a point of maximum potential energy stored inboth the first and second springs.
 11. A bracing system comprising: anelongate shaft having a first shaft portion in a reciprocatingrelationship with a second shaft portion along a long axis that extendsthrough the first and second shaft portions and a short axis that isorthogonal to the long axis; a first brace having: a switch that ismoveable between an engaged orientation and a disengaged orientation; afirst contact portion configured to be contacted by the first shaftportion as the first shaft portion moves along the long axis past theswitch in a first direction and, as a result of that contact, the switchmoves from the engaged orientation to the disengaged orientation; asecond contact portion configured to be contacted by the first shaftportion as the first shaft portion moves along the long axis past theswitch in a second direction and, as a result of that contact, theswitch moves from the disengaged orientation to the engaged orientation;a bracing member carried by the switch and having a tip that, when theswitch is in the engaged orientation, is located immediately adjacentand laterally braces the second shaft portion by limiting movement ofthe second shaft portion along the short axis and, when the switch is inthe disengaged orientation, is not located immediately adjacent theshaft.
 12. The system of claim 11 further comprising: a second bracelocated adjacent the shaft and opposite the first brace, wherein thesecond brace rotates between the engaged and disengaged orientationssimultaneously with and in an opposite direction of rotation to thefirst brace, wherein, in the engaged orientation, the bracing member ofthe first brace limits movement of the second shaft portion along theshort axis in a third direction and the bracing member of the secondbrace limits movement of the second shaft portion along the short axisin a fourth direction.
 13. The system of claim 11 further comprising aspreader for assisting the switch to rotate between the engagedorientation and the disengaged orientation, the spreader having:tapering sides that contact the first contact portions of both the firstand second braces as the first shaft portion moves along the long axispast the switch in the first direction and that contact the secondcontact portions of both the first and second braces as the first shaftportion moves along the long axis past the switch in the seconddirection, wherein the first contact portions of the first and secondbraces are guided along the tapering sides as the first shaft portioncontinues to move in the first direction which automatically rotates theswitch from the engaged orientation to the disengaged orientation andthe second contact portions of the first and second braces are guidedalong the tapering sides as the first shaft portion continues to move inthe second direction which automatically rotates the switch from thedisengaged orientation to the engaged orientation.
 14. The system ofclaim 11 further comprising a position sensor configured to sense theposition of the switch.
 15. The system of claim 14 further comprising acontroller for controlling an amount of pressured applied along the longaxis of the elongate shaft, wherein a maximum amount of pressure thatmay be applied along the long axis of the elongate shaft is at leastpartially determined by the sensed position of the switch.
 16. Thesystem of claim 15 wherein the position sensor sends a signal to thecontroller when an amount of pressure applied along the long axis of theelongate shaft for a selected position of the switch meets or surpassesa predetermined limit and wherein that warning signal triggers at leastone of: an audible alert generating by an audible alarm connected to thesystem, a visual alert generated by a visual alarm connected to thesystem, a reduction pressure applied along the long axis of the elongateshaft, a shutdown of the system.
 17. The system of claim 11 wherein thefirst shaft portion and the second shaft portion are joined end to endand move together as a single unit along the long axis.
 18. The systemof claim 11 wherein the first shaft portion is slidably engaged with thesecond shaft portion and moves with respect to the second shaft portion.19. The system of claim 11 wherein the second shaft has a diameter thatis smaller than a diameter of the first shaft.